This directory contains data for the ISS-RapidScat Level 2B 12.5km science-quality Version 1.1 netCDF dataset. ************************************************** Dataset description: This dataset contains the RapidScat Level 2B 12.5km Version 1.1 science-quality ocean surface wind vectors. The Level 2B wind vectors are binned on a 12.5 km Wind Vector Cell (WVC) grid and processed using the Level 2A Sigma-0 dataset. RapidScat is a Ku-band dual beam circular rotating scatterometer retaining much of the same hardware and functionality of QuikSCAT, with exception of the antenna sub-system and digital interface to the International Space Station (ISS) Columbus module, which is where RapidScat is mounted. The NASA mission is officially referred to as ISS-RapidScat. Unlike QuikSCAT, ISS-RapidScat is not in sun-synchronous orbit, and flies at roughly half the altitude with a low inclination angle that restricts data coverage to the tropics and mid-latitude regions; the extent of latitudinal coverage stretches from approximately 56 degrees North to 56 degrees South. Furthermore, there is no consistent local time of day retrieval. This dataset is provided in netCDF-4 "classic" format and made available via FTP and OPeNDAP. For data access, please click on the "Data Access" tab above. This Version 1.1 dataset differs from the previous Version 1 dataset as follows: 1) A new neural network approach for high wind speeds provided rain corrections for the "retrieve_wind_speed" variable for wind speeds in excess of 15 m/s. 2) The data variables containing the number of measurements of each type for each wind vector cell have been corrected; these variables include "number_in_aft", "number_in_fore", "number_out_aft", and "number_out_fore". 3) The "wind_obj" data variable has been corrected to include the proper data for the conditional probability for the objective DIRTH function values. It is advised for users to avoid using the "wind_obj" variable in this dataset since it is minimally applicable and meant primarily for quality assurance; for users who wish to access the objective function values for each ambiguity, it is suggested to use only the "ambiguity_obj" variable. The "wind_obj" variable contains DIRTH probabilities (which are derived form the "ambiguity_obj" objective function values) in the range of 0 to 1 indicating the conditional probability that the true direction is within + or - 2.5 degrees of the retrieved wind direction given the observed backscatter measurements in the cell. The complete dataset description and metadata record is made available on the PO.DAAC web portal: http://podaac.jpl.nasa.gov/dataset/RSCAT_LEVEL_2B_OWV_COMP_12_V1.1 ************************************************************************************* Cautionary Notes: 1) It is advised for users to avoid using the "wind_obj" variable since it is minimally applicable and meant primarily for quality assurance; for users who wish to access the objective function values for each ambiguity, it is suggested to use only the "ambiguity_obj" variable. 2) Due to the multi-operational roles of ISS, disruptions in the data flow and data retrieval for RapidScat occur much more frequently than stand-alone remote sensing platforms. Users depending on the availability of data within the last 14 days are therefore advised to defer to the near-real time updates provided by the following link at NOAA for adequate and timely information regarding any planned or ongoing data outages: http://manati.star.nesdis.noaa.gov/rscat_images/monitor/RapidScat_Scheduled_Outages.txt ************************************************************************************* Known Issues with RapidScat: 1) 25 April 2015 (orbit range: 3333-4157) - ISS spacecraft experienced changes in attitude in excess of the nominal spacecraft attitude for RapidScat wind retrieval in comparison to the previous portion of the mission. - As a result, the quality of the data was disrupted and the data for the above orbital revs was quarantined. - After the issue was corrected, the quarantined data was replaced with corrected versions which were then published on the FTP and OPeNDAP sites as of 19 June 2015. - The issue was resolved on 17 June 2015. - A summary of the changes and issues with the data files corresponding to the above orbital revs include the following: * Invalid VV-pol fore pulses near the nadir track are now correctly flagged as invalid and not used in wind retrieval or quality flagging. * Whole pulses are no longer flagged as invalid when any science slices in that pulse are not constrained to be on the surface of the Earth. This affected HH-aft observations near the nadir track. * Adapted the rain-flagging to work in portions of the swath where one outer beam look is missing. - The above corrections were shown to improve the wind retrieval accuracy and reduce the number of rain-flagged data to the nominal percentage as well as enable the RapidScat Project to rain-flag the portions of the swath where the VV-pol fore pulses are missing. - The ISS spacecraft attitude anomaly was persistent through 23 July 2015. - For more details, please refer to: http://podaac.jpl.nasa.gov/announcements/2015-06-19_RapidScat_L2B_Data_Quality_Disruption 2) 15 August 2015 (orbit range: 5064-5615): - At 03:01:59 UTC there was an anomalous drop in the echo power signal in the receiver of approximately 20 dB. - Both noise and signal power dropped but not by equal amounts. The Signal to Noise Ratio dropped by 10 dB. - Corresponding with this drop in power was an increase of approximately 0.20 mA in current in the Scatterometer Electronics Subsystem (SES). - Due to this anomaly the RapidScat Science Data Systems Team was initially unable to process the telemetry data to backscatter (Level 1B, 2A) or wind vectors (Level 2B). - The precise cause of the "reduced echo power" anomaly has not yet been determined. - Wind direction (and to a lesser extent speed) accuracy are degraded for low winds. Winds above 6 m/s are not significantly affected but statistics for 3-6 m/s are noticeably worse especially in the middle of the swath. - Rain flagging is now unavailable for the outer (single beam portion) of the swath. The IMUDH rain flag that the JPL wind retrieval has been using is corrupted because it uses the RapidScat Brightness temperature. With a 10 dB loss in SNR, brightness temperatures are no longer usable. So we are switching rain flags to use the Impact Quantity Rain flag which has been previously utilized to determine when to correct wind speeds for rain. The new rain flag does not use brightness temperature and is not available in the outer swath. The statistics of the rain impact quantity have not changed significantly as a result of this anomaly. - Beginning with data from orbital rev 5064, the previously improved rain speed correction for tropical cyclones (version 1.1) has now been turned off because it relies on brightness temperature. The Version 1.1 L2B processing has therefore reverted back to the original rain correction used in the Version 1.0 L2B processing. - Even though processing has been reverted back to what was used for Version 1.0, all data files will continue to be referenced as Version 1.1 or v1.1. - As a result of this anomaly, calibration activities are on-going in the hopes of providing a future re-processed dataset with a consistent calibration for all SNR states. 3) 18 September 2015 (orbit range: 5615-5880) - RapidScat Reduced Echo Power Restored to Pre-Anomaly Levels - More details are available here: http://podaac.jpl.nasa.gov/announcements/2015-09-24_RapidScat_Reduced_Echo_Power_Restored 4) 6 Octover 2015 (affected orbits: 5881, 5882, 5883, 5884, 5885, 5886, 5888, 5891, 5892, 5893, and 5894) - RapidScat Reduced Echo Power Anomaly Recurrence - More details are available here: http://podaac.jpl.nasa.gov/announcements/2015-10-20_RapidScat_Reduced_Echo_Power_Anomaly_Recurrence 5) 24 December 2015 (orbit range: 7084-7297) - RapidScat Wind Observation Data Flow Disruption - More details are available here: http://podaac.jpl.nasa.gov/announcements/2015-12-29_RapidScat_Wind_Observation_Data_Flow_Disruption 6) 5 January 2015 (orbit range: 7297-present) - RapidScat Data Disruption Restored - More details here: http://podaac.jpl.nasa.gov/announcements/2016-01-08_RapidScat_Data_Disruption_Restored 7) 17 February 2016 (orbit range: - RapidScat Data Flow Disruption - More details here: http://podaac.jpl.nasa.gov/announcements/2016-03-01_RapidScat_Data_Flow_Disruption_February 8) 10 March 2016 (orbit 08307) - This is the data file produced for this dataset. - Users who wish to gain access to data beyond this period should go to: ftp://podaac.jpl.nasa.gov/allData/rapidscat/L2B/v1.2/ 9) 19 August 2015 to 10 March 2016 (orbit range: 05127 to 08307) - Version 1.2 is available using optimally calibrated Sigma-0 for low SNR. - Users who wish to gain access to data Version 1.2 data should go to: ftp://podaac.jpl.nasa.gov/allData/rapidscat/L2B/v1.2/ Note: for users who wish to gain more information on instrument/spacecraft anomalies and outages, please refer to: http://manati.star.nesdis.noaa.gov/rscat_images/monitor/RapidScat_Scheduled_Outages.txt ************************************************************************************* Directory contents (data files partitioned according to 4-digit years): /2014.../2016 Note: The actual data files are contained within an additional layer of 3-digit day-of-year directories. File naming convention: rs_l2b_v1_RRRRR_YYYYMMDDHHmm.nc.gz rs_l2b Instrument/Level Identifier: RapidScat Level 2B RRRRR 5-digit orbital revolution number v1 Version ID: v1 = version 1 YYYY 4-digit year of data file creation date MM 2-digit month of data file creation date DD 2-digit day of month of data file creation date HH 2-digit hour of 24-hour day of data file creation time mm 2-digit minute of hour of data file creation time nc File extension: nc = netCDF gz GNU Zip file extension ************************************************************************************* Please send any comments or questions to https://podaac.jpl.nasa.gov/forum/. Last modified on 4 May 2016.